How to create forbidden love between opposing families/groups

• Different racial familes- Two families, one Indian, one British. The daughter of the Indian family is arranged to marry another Indian boy, however her family's plan for her goes wrong when she falls in love with the son of a white British family. 
• Different religions- Two families, one Christian and one Atheist. The children of the families fall in love.
• Different political views- Two families, one at the head of the Labour party, the other the head of the Conservative party. The children of the opposing political familes fall in love. 
• Different gangs- Two rival gangs, fighting for control of the city. Two opposing members of the gangs fall in love. 
• Different classes- Two children of opposite ends of the class system fall in love. 
• Different sport teams- Two members of rival sport teams fall in love. 
• Different sides of the law- Two families, one law enforcing family, one criminal family. The children of each of the families fall in love. 
• Different business companies- The children of two rival family based business companies fall in love.